Iron Homeostasis

Question 1

How is iron stored?

Answer 1

• Ferritin is soluble form, meanig iron is readily available

- Haemosiderin is insoluble conglomerates of ferritin, meaning iron is slowly available

Question 2

How is iron transported around the body?

Answer 2

Bound to transferrin - binds to transferring receptors on RBCs (80%) and Heptocytes (20%)

Question 3

Where and how is iron absorbed?

Answer 3

Absorbed mostly in duodenum, but also some in jejunum. Haem iron (from red meat) is easily absorbed.
Non-haem iron (white meat and veg) must first release the iron by acidic digestion and proteolytic enzymes and then reduce it from ferric to ferous form by dueodenal cytochrome b1 (influenced by vitamin C)

Iron is absorbed into the enterocytes via divalent metal transporter (DMT1) and then into the circulation via ferroportin

Question 4

Where is ferroportin located and why?

Answer 4

Enterocyte - iron transport into circulation

Macrophages - iron release

Question 5

What are the causes for Iron deficiency anaemia?

Answer 5

In males and post-menopausal women, due to GI blood loss unless proven otherwise

In pre-menopausal women, due to menstruation or pregnancy

Question 6

What are the causes for haematinic deficiency in Coeliac disease?

Answer 6

Folate deficiency

Iron deficiency

Vitamin B12 deficiency - unlikely

Question 7

Describe the regulatory mechanism of iron metabolism and how HHC affects this

Answer 7

Hepcidin is produced in the liver in response to raised plasma iron or trasnferrin. It binds to ferroportin and degrades it, preventing the transfer of iron into circulation and release of iron from macrophages.

Hepcidicin production requires the expression of the HFE gene, which if mutated, as in HHC, results in decreased hepcidin production. This therefore results in iron overload

Question 8

What is HHC

Answer 8

Hereditary Haemachromatosis - autosomal recessive disorder of iron metabolism which causes iron overload.

Question 9

What happens to transferrin in HHC?

Answer 9

Due to iron levels getting so high, transferin production is switched off, resulting in over saturation of transferrin

Question 10

What are the consequences of HHC?

Answer 10

Excess iron travels to different areas, causing consequences:

• Liver - Cirrhosis
• SKin - brozing
• Pacreas - diabetes
• Joints - arthritis
• Heart - Cardiomyopathy

Question 11

How is HHC treated?

Answer 11

Venesection

Question 12

What is sideroblastic anaemia

Answer 12

Iron gets to mitochondria but due to a blockage, cannot escape so therefore iron content cant increase.